Previous Year Question

Lichens are highly useful Bioindicators of air quality. An organism is used as a Bioindicator when its presence, absence, abundance or physiological condition provides information about environmental quality.

A Lichen is not a single organism. It is generally a symbiotic association between a Fungus and a photosynthetic partner—Green Alga or Cyanobacterium. The fungal component is called the Mycobiont, while the photosynthetic component is called the Photobiont.

Lichens do not possess well-developed roots and protective cuticles like higher plants. They absorb moisture and dissolved substances directly from the atmosphere. Therefore, atmospheric pollutants can also readily enter their tissues.

Many Lichen species are particularly sensitive to Sulphur Dioxide (SO₂) and other atmospheric pollutants. Consequently, their diversity and abundance can provide information about long-term air quality in an area. The Botanical Survey of India also identifies Lichens as extensively used bioindicators of air quality and in biomonitoring.